The correlated study of intracellular metabolic interactions and intercellular communication (W. LOEWENSTEIN, Arch. Inter. Med. 129: 305, 1971) is possible through refined temporal, optical & spectral resolution of microspectrofluorometry, specially geared to the multichannel probing of compartments within the living cell (e.g. ascites cells, liver or liver tumor cells in culture), via the blue fluorescence of reduced NAD(P), also flavins, structural, conformational or ion probes (in conjunction with electrophysiological techniques). Presently two-channel microfluorometry (Biochim. Biphys. Acta 286: 182 (1972) based on electronic chopping and microelectrophoretic addition of dyes or metabolites, is being used to study intracellular transport or to unravel (via NAD(P) reduction-reoxidation transients) phase relationships or metabolic lags between various intracellular compartments. Multichannel fluorescence scan of the living cell or spectral scan (based on an electron bombardment silicon camera tube in conjunction with a multiscaling computer) can allow the probing of intracellular enzyme-substrate reactions, organelle interactions or metabolite and ion distribution. It provides also a unique method for the study of coordinated metabolic activity (or transfer of metabolites across junctional membranes) among various members of a cell colony. Various applications are considered, including comparative observations during phases of the cell cycle, as well as between normal, differentiating, embryonic, transformed & malignant cells, hybrids (also hopefully clinical-pathological material). While "laser microfluoremetry" may allow a time resolution so far unattained in the study of intracellular enzyme kinetics or conformation, selective alteration of cell organelles by laser techniques is also possible for such studies.